This invention relates to a test plate apparatus suitable for promoting fluid interactions such as by growing cells in a nutrient liquid within a multiplicity of wells. More particularly, this invention relates to such a test plate apparatus which permits adding or removing liquid from wells in the test plate without disturbing the material such as cells within the wells.
At the present time, multi-well test plates are provided wherein the wells have a circular shape and size which permits the introduction therein of a tubular member having a membrane upon which cell attachment, growth and differentiation occurs. The microporous member allows free diffusion of ions and macromolecules between cells and their apical and basolateral surfaces through a liquid medium which surrounds the tubular member and which permeates the membrane. The test plates containing the wells are rectangular and having a standard size of about 3.25 inches by 5 inches in order to accommodate standard analytical apparatus. Since the plate size is define and since it is desired to avoid corners in the wells to avoid liquid stagnation areas, the wells are circular. In addition, the clearance between the interior well wall and the outside wall of the tubular member insert is minimized. The member insert is generally as large as possible to maximize the cell growth-area which leads to a lower error in the data gathering. However, a balance exists in that the basal and apical fluid volumes should be as close to for easy pipeting, to minimize fluid pressure between inner and outer wells and as large as possible to reduce the frequency of pipetting. This space requirement renders it difficult to insert pipetting means into the well to remove or add liquid while the tubular member is positioned within the well. The periodic removal of liquid to remove cell waste and additions of liquid to provide cell nutrients is required to maintain cell viability. In addition, cell based assay protocols require fluid manipulation. In addition, automatically controlled pipetting means cannot be used since the tubular member position is random and the probability that the pipetting means would damage the cells and pierce the membrane is high.
Thus, it is presently necessary to pipette manually in order to avoid cell damage by the pipetting apparatus. This procedure is time-consuming, since it generally requires individual well treatment and is undesirable, since it may cause cell damage. Accordingly, it would be desirable to provide a test plate arrangement which permits removing or adding liquid from or to wells in the cell plate which permits the use of standard automatic pipetting means.